Lexus RX300 (MCU15). Manual — part 41

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ENGINE — 1MZ-FE ENGINE

37

3. Intake Manifold

D The port diameter of the intake manifold has been increased and the port length has been optimized

to improve engine performance.

D An engine coolant passage connects the left and right banks at the rear end of the intake manifold.

D The intake manifold gasket has rubber coating applied onto surface, and provide superior durability.

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A – A Cross Section

B – B Cross Section

Engine
Coolant
Passage

A

A

B B

Outer Side

z

! Intake Port

Side

Rubber Coating

4. Exhaust Manifold

A stainless steel exhaust manifold is used for improving the warm-up of the three-way catalytic converter
and for weight reduction.

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Right Bank
Exhaust Manifold

Gasket

Left Bank
Exhaust Manifold

Gasket

ENGINE — 1MZ-FE ENGINE

38

5. Exhaust Pipe

D A ball joint has been adopted for the connection between the front exhaust pipe and the center exhaust

pipe, as well as between the center exhaust pipe and the tailpipe to reduce vibration.

D A 2-way exhaust control system has been adopted to improve engine performance and ensure an even

quieter operation.

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Ball Joint

Tail Pipe

Sub Muffler

Center Exhaust Pipe

Front Exhaust Pipe

TWC

3

2-Way Exhaust Control System

D This system reduces the back pressure by opening and closing a control valve that is enclosed in the main

muffler, thus varying the exhaust gas passage.

D The valve opens steplessly in accordance with the operating condition of the engine, thus enabling a

quieter operation at lower engine speeds, and reducting back pressure at higher engine speeds.

1) Construction

The control valve is enclosed in the main muffler. When the exhaust gas pressure overcomes the spring
pressure, the control valve opens steplessly in accordance with the exhaust gas pressure.

2) Operation

a. When Control Valve is Closed (low engine speed)

Since the pressure in the main muffler is low, the control valve is closed. Hence exhaust gas does
not pass the bypass passage, and exhaust noise is decreased by the main muffler.

b. When Control Valve is Open (middle to high engine speed)

The control valve opens more as the engine speed and the back pressure in the muffler increase. This
allows a large volume of exhaust gas to pass the bypass passage, thereby substantially decreasing the
back pressure.

Control Valve Closed

Control Valve Open

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Exhaust
Gas

Control Valve

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ENGINE — 1MZ-FE ENGINE

39

JFUEL SYSTEM

1. Air Assist Fuel Injection System

This system is designed to regulate air intake to the upperstream (atmospheric side) of the throttle valve
using the ISC valve, and direct it to the nozzle of the fuel injector inside the intake manifold (negative
pressure side). This promotes atomization of the fuel while reducing emissions and improving fuel economy
and idle stability.

Injector

Injector

Intake Manifold

Air Pipe

Throttle Valve

Air Flow Meter

Air Cleaner

ISC Valve

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2. Fuel Returnless System

This system is to reduce the evaporative emission. As shown below, integrating the pressure regulator
and fuel filter with the fuel pump assembly made it possible to discontinue the return of fuel from the
engine area and prevent temperature rise inside the fuel tank.

Pulsation
Damper

Fuel
Pump

Fuel Filter

Pressure
Regulator

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ENGINE — 1MZ-FE ENGINE

161ES45

Plug Cap

Igniter

Ignition Coil

40

JIGNITION SYSTEM

1. General

A DIS (Direct Ignition System) has been adopted in the 1MZ-FE engine. The DIS improves the ignition
timing accuracy, reduces high-voltage loss, and enhances the overall reliability of the ignition system by
eliminating the distributor.
The DIS in 1MZ-FE engine is an independent ignition system which has one ignition coil for each cylinder.

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VVT Sensors

Camshaft
Position
Sensor

Crankshaft
Position
Sensor

Various
Sensors

VV1, 2

NE

Engine

ECU

IGT1

IGT2

IGT3

IGT4

IGT5

IGT6

IGF

+B

Ignition Coil (with Igniter)

No. 1 Cylinder

No. 2 Cylinder

No. 3 Cylinder

No. 4 Cylinder

No. 5 Cylinder

No. 6 Cylinder

2. Ignition Coil

A compact and cylindrical ignition coil with a built-
in igniter has been adopted.
Shaped in such a way that it can be placed directly
over the spark plug, the ignition coil is installed in
the spark plug hole of the cylinder head.
As a result, the high-tension cords are no longer nec-
essary and high-voltage loss and electromagnetic in-
terference have been reduced.

3. Spark Plug

Iridium-tipped spark plugs have been adopted to improve ignition performance while maintaining the same
level of durability of the platinum-tipped spark plugs.